From 44af23c162c7c80d5578c83ac5bfe0c9b32bd58c Mon Sep 17 00:00:00 2001
From: Zlatin Balevsky <zlatinb@gmail.com>
Date: Sat, 19 Sep 2020 17:28:19 +0100
Subject: [PATCH] restrict forwarding of queries to sqrt of neighboring
 connections.  Thanks to 'qtm' for the idea

---
 .../connection/UltrapeerConnectionManager.groovy     | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/core/src/main/groovy/com/muwire/core/connection/UltrapeerConnectionManager.groovy b/core/src/main/groovy/com/muwire/core/connection/UltrapeerConnectionManager.groovy
index ef9736f6..0e60a360 100644
--- a/core/src/main/groovy/com/muwire/core/connection/UltrapeerConnectionManager.groovy
+++ b/core/src/main/groovy/com/muwire/core/connection/UltrapeerConnectionManager.groovy
@@ -21,6 +21,8 @@ class UltrapeerConnectionManager extends ConnectionManager {
 
     final Map<Destination, PeerConnection> peerConnections = new ConcurrentHashMap()
     final Map<Destination, LeafConnection> leafConnections = new ConcurrentHashMap()
+    
+    private final Random random = new Random()
 
     UltrapeerConnectionManager() {}
 
@@ -44,8 +46,16 @@ class UltrapeerConnectionManager extends ConnectionManager {
         if (e.replyTo != me.destination && e.receivedOn != me.destination &&
             !leafConnections.containsKey(e.receivedOn))
             e.firstHop = false
+        final int connCount = peerConnections.size()
+        if (connCount == 0)
+            return
+        final int treshold = (int)(Math.sqrt(connCount)) + 1
         peerConnections.values().each {
-            if (e.getReceivedOn() != it.getEndpoint().getDestination())
+            // 1. do not send query back to originator
+            // 2. if firstHop forward to everyone
+            // 3. otherwise to randomized sqrt of neighbors
+            if (e.getReceivedOn() != it.getEndpoint().getDestination() &&
+                (e.firstHop || random.nextInt(connCount) < treshold))
                 it.sendQuery(e)
         }
     }